whenever there is an election or a referendum they're afraid of the ballot box. it is because they know the people are not on their side. >> reporter: tahrir square was far from full today. egypt's had its revolution and that, for many, will suffice. yet the president's opponents say another may now be required. >> ( translated ): we didn't have a revolution just to return to the era of mubarak and worse. >> ( translated ): mohamed morsi has divided the nation. we want him to fall. along with the muslim brotherhood because they are traitors. >> reporter: last night, muslim brotherhood offices were set on fire outside cairo. and crowds with these demands are now gathering again outside his palace. >> sreenivasan: three more officials announced their resignation in wake of the violence. late today, in a televised speech, president morsi called for a comprehensive and productive dialogue. but he also accused some of the opposition of serving the old mubarak regime. and he insisted a referendum on the constitution would go ahead on december 15. margaret warner takes